Electrical apparatus and method



Feb. 15,1927. C. G' SMITH- ELECTRICAL APPARATUS` AND METHOD` Original Filed April 25. 1921 Patented Feb. 8, 1927.

UNITED STATES CHARLES G. SMITH, 0F MEDFORD, MASSACHUSETTS, ASSIGNOR, BY MESNE PATENT QFFICE.

ASSIGN- MENTS, T0 RAYTHEON MANUFACTURING COMPANY, 0F CAMBRIDGE, MASSACHU- SETTS, A lC0RPOIELA'JJIIOII' 0F MASSACHUSETTS.

ELECTRICAL APPARATUS AND METHOD.

Application led April 25, 1921, Serial No. 464,358. Renewed November 22, 1926.

The present invention relates to electrical apparatus and more particularly to apparatus of the type disclosed in the co-pending applications of Smith Serial No. 415,536,"

iiled October 8, 1920, and Serial No. 418,263, filed October 20, 1920.

The mean Afree path of an electron in a gas, as herein meant` is the average distance which an electron travels under the influence of an electric eld impressed on the gas before ionizing impact with a gas molecule (or atom). If the potential dierence through which the electron passes is sufiiciently great to bring the electron up to ionizing speed before impact, ionization will take place, the collision in this case resulting in more electrons and positive ions being given ofi' from the gas molecule, the positive ions passing to the cathode and releasing further electrons this process being cumulay tive and sustaining gaseous conduction. The

electrical conduction through the gas increases With its pressure and the mean tree path of an' electron becomes progressively shorter with increases in pressure.

It is the object of the present invention to improve tubes of the character described in such a manner that the potential drop through the tube may be reduced, the permissible gas pressure increased, and other advantages obtained.

With this object in View it is found that by the-employment of an inertmonatomic gas Within the tube, such as helium, neon or argon, the potential drop through the tube may be substantially reduced and the allowable gas pressure increased. ,The use of an inert monatomic gas such as helium is exceedingly important as in the first place the electrons in these gases have a mean free path which is so long that a helium filled tube may be successfully operated at a pressure many times as great as the permissible pressure if air or a similar gas were employed. In. addition the use ot helium and similar inert gases is important as these gases do not react chemically with the materials of the tube and cause changes in gas pressure.

A further feature of the present lnvention consists-in the use of an absorbent material such as gas-mask charcoal inl communication with the helium er other gas to absorb and helium may eventually be absorbed by the electrodes during the operation of the tube. In the simplest embodiment of the invention which has yet been devised the charcoal is located directly in the tube itself where it absorbs impurities from the helium during the filling of the tube and is'thereafter in readiness during the operation of the tube to stabilize the pressure to a certain extent. In the accompanying drawings illustrating the preferred form of the invention Fig. 1 represents an elevation partly in section of a tube embodying the principles of the invention; Fig. 2 is a sectional elevation of the electrodes; and Fig. 3 is a diagram illustrating theform of circuit in which the tube is embodied as a rectiiier.

Referring to the illustrated embodiment of the invention a gas filled receptacle l0 receives cooperating electrode members 12 and 14 which are in the form of concentric cylinders supported at opposite ends of the l receptacle 10. The inner electrode cylinder 12 has a reduced portion 16 extending within a cooperating cylinder and a larger portion 18 of approximately the diameter of the outer cylinder, this portion of larger diameter being connected with supporting members 20 which areV in turn connected With a base member 22 at one end of the receptacle. The outer cylinder 14 is supported from the opposite end of the receptacle through supporting wires'24 which emerge from a base member 26 projecting from the end ofthe receptacle. The electrode cylinders are connected with leads 30 and 81 respectively, the two leads extending from' opposite ends of the tube 10,. A magnetic field is introduced in the space separating the two cylinders and is localized through the provision of iron or steel tubes 32 and 33 received within the outer electrode cylinder 14, as indicated'in Fig. 2, and separated at their inner ends in order to localize the magnetic field in a manner which will be obvious to those skilled in the art. The magnetic eld may be conveniently Vcreated by. a permanent 'magnet indicated at 36.

This tube is filled with helium or a similar inert monatomic gas which may be at a pressure of approximately one-half acentimeter which, as stated lreviously, is many times the pressure whic may be employed with air or with active gases such as oxygen, nitrogen and hydrogen. This permissible high pressure simplifies the filling of the tube and in addition has the distinct advantage that if a small absolute amount of helium or other gas condenses upon the walls of the tube or is absorbed by the electrode the change in the relative pressure of the gas is very small as compared with the change which would result if a substantially lower pressure were employed. One end of the receptacle contains gas-mask charcoal 40 which may be retained in place by glass wool, indicated at 42. This charcoal readily absorbs the active gases which may be contained in the monatomic gas as an impurity but only feebly absorbs the pure inert gas, enabling the tube to be absolutely freed from everything except the inert gas. The employment of this charcoal is not only advantageous in initially freeing the helium from impurities but, in addition, acts as a reservoir to absorb any active gases which may be evolved from the electrodes during the operation of the tube. Fig. 3 illustrates a simple form of circuit embodying the tube as a rectifier and comprising an input circuit, indicated at 44, capable of delivering alternating current to the primary of a step-up transformer 46, the

secondary of which is embodied in an output circuit containing the tube, which rectifies the high voltage alternating current delivered thereto. This output circuit may be connected with any desired form of load circuit (not shown) to'utilize the high voltage ycurrent so rectified.

While it has been proposed to lower the voltage drop in discharge tubes by using inert gas, l Ybelieve l am the first to discover that, in short-path tubes embodying the mean free path principle as disclosed herein,

t and in my aforesaid applications, the spac- As more fully described in my copending applications, the outer electrode 14 oonsti-- tutes a hollow cathode from which electrons may travel, whenl 14 has negative polarity, along paths which are longer than the short,- est distance between the electrodes, thereby causing ionization which permits gaseous -conduction between the electrodes during each half-cycle when 14 is negative.

I have found that in the operation of this. invention the ,inonatomic gas, at a pressure of the order of that above mentioned, prevents clean-up, that is prevents the 'gas pressure from decreasing during operation. This I believe to be due to' adhesion to the cathode surface of a layer of the gas sufficiently thick to protect the surface from ion bombardment so that ygas molecules are not permanently entrapped in the cathode surface during operation. This Jfunction of the gas is ofcourse peculiar to non-thermionic tubes in which the cathode functions below the temperature at which the operation is dependent upon thermionic emission from the cathode since in thermionic tubes employing incandescent filaments or hot spots the cathode is not subjected to ion bombardment of suflicient velocity to cause clean-up and an incandescent cathode will not permanently retain gas.

The terms bi-lateral conduction lbetween the electrodes of course means conduction in bothvdirections across the gas gap and unilateral conduction mea-ns conduction substantially' in one direction only.

I claim: f

1. Electrical apparatus of theptype having electrodes with a gas space therebetween which is restricted in length substantially to the mean free path of electrons therein for 105 restricting gaseous conduction between the electrodes. characterized by means for inn creasing the permissible length of said space over the length in air at the same pressure for a corresponding degree of restriction of 110 gaseous conduction, said means comprising monatomic gas in said space. f

2. Electrical apparatus ofthe type having electrodes with a gas space therebetween which is restricted in length substantially U5 to the mean free :path of electrons therein for restrictingr gaseous ,conductionbetween the electrodes` characterized by means for increasing the permissible length of said space over the length in air at the same pres- 120 sure for a corresponding degree of vrestriction of gaseous conduction, said means comprising monatomic gas in said space, and means comprising differently shaped elezr- Y trode surfaces permitting gaseous conduc- 12" tion between the electrodes in one direction.

3. Electrical apparatus of the type having electrodes with a gas space therebetween which is restricted in length substantially to the mean free path of electrons therein 130 for iestricting gaseous conduction between the electrodes, characterized by. means for increasing the` permissible length of said space over the length in air at the same pressure for a corresponding degree'of. restriction of aseous conduction, said means comprising elium in said space.

4. Electrical apparatus of the type having v electrodes with a gas space therebetween which is restricted in length substantially to the mean free path of electrons therein for restricting gaseous conduction between the electrodes, characterized by means for increasingthe permissible length of said space over the length in air at the same pressure for a corresponding degree of restriction of gaseous conduction, said means comprising helium in said space, and means comprising di'erently shaped electrode surfaces per mitting gaseous conduction between the electrodes in one direction while restraining conduction in the opposite direction.

5. -Electrical apparatus comprising electrodes with a gas space therebetween which is comparable in length to the mean free path of electrons therein for resisting gascous conduction between the electrodes, and means for increasing the permissible gas pressure in said space over that pressure oi air, in a space of the same length, which affords corresponding restriction of gaseous conduction, said means comprising` monatomic gas molecules substantially to the eX- clusion of air molecules.

6. Electrical apparatus comprising electrodes with a gas space therebetween which is comparable in length to the mean free path of electrons therein for'restricting gas.

cous conduction between the electrodes, means for increasing the permissible gas pressure in said space over that pressure ott air, in a space of the same length, which aiords corresponding restriction of gaseous conduction, said means comprising mon-` atomic gas molecules substantially to theexclusion of air molecules, and means permitting gaseous conduction between the electrodes in one direction Without preventing substantial conduction in the opposite direction.

7. Electrical discharge apparatus of the type requiring gas in the space between the electrodes for conduction' therebetween under normal conditions of operation, means for restricting conduction between the electrodes in one direction comprising an arrangement of the electrodes such that the gas space therebetween is comparable in length to the mean free path of electrons in the gas, and means for increasing the permissible gas pressure in said space over that pressure of air, in a space of the same length, which affords corresponding restriction of gaseous conduction, said last means compr1s1ng monatomic gas 1n said space.

8. Electrical dscharve apparatus of the type. requiring gas in t e s ace between the.

electrodes for conduction't erebetween un.

der normal conditions of operation, means for restricting conduction between the elec# trodes in one direction comprising an-"ar rangement of the electrodes such that the as space therebetween4 is com arable in ength to the mean free path o electrons in the gas, means lfor increasing the permissible gas pressure in said space over that pressure of a1r,.in a'space of the same length, which aords corresponding restriction of gaseous conduction, said last means comprising -monatomic gas in said space, and means whereby electrons leaving one electrode are caused to travel in paths longer than the shortest distance between the electrodes, thereby causing ionization which permits conduction in one direction.

9. An electrical apparatus comprisln-g electrodes immersed in an inert monatomic gas and having surfaces spaced apart a distance comparable to the mean free ath of electrons in the gas and arranged or gaseous conduction from one electrode' to the other under conditions which restrain conduction in the opposite direction,` the inert monatomic gas serving to increase the permissible spacing between said surfaces.

10. An electrical apparatus comprising electrodes immersed in an inert monatomic gas and having opposing surfaces spaced apart a distance which 1s short and comparable to the mean' free path of electrons in the gas, means for creating an electric field between the electrodes, and means for lengthening the paths of electrons impelled by the electric field Ito distances which are suliiciently long to initiate conduction, the inert monatomlc gas serving to increase the permissible spacing between said surfaces.

spaced a distance comparable to the mean free path of electrons in the gas at said pressure, and means within the sealed tube for automatically compensatingfor gas absorption due to operation of the tube, whereby the mean free path of the electrons is maintained approximately constant.

13. An electrical apparatus comprising a sealed tube containing gas at a predetermined pressure, electrodes having surfaces spaced a` distance comparable to the mean free path ot electrons in the .was at said pressure, and porous material Khavin absorbed therein a quantity of gas su cient to compensate for gas absorption due to normal operation o the tube for a long` period of time, whereby the mean tree path of the electrons ismaintained approximately constant.

14. A rectifier comprising a cathode and an anode with a as space therebetween comparable in lengt tb the mean free path of electrons in the gas for restricting gaseous conduction therebetween, means for increasing the permissible spacing of the electrodes comprising monatonnc gas in said space, and means comprising di'erently shaped electrode surfaces permitting gaseous conduction between the electrodes in one direction, said cathode being hollow and so related to the anode that electrons may travel from the interior thereof along paths longer than said length. l

15. A rectifier comprising a cathode and an anode, means tor restricting conduction between the electrodes comprising a gas space comparable to the mean free path of electrons in the gas, means for increasing the permissible-pressure in said space comprising inert monatomic gas, and means comprising dili'erently shaped electrode surfaces permitting gaseous conduction between thc electrodes in one direction, said cathode being hollow and so related .-to the anode that electrons may travel from the interior thereof along paths longer than the shortest` distance between the electrodes.

16. In electrical apparatus having electrodes separated by a gas space comparable y in length to the mean tree path of electrons Cil in the gas for restricting gaseous conduction between the electrodes; the method which comprises increasing the permissible gas pressure in the space over that pressure of air, in a space of the same length,"which affords corresponding restriction of gaseous conduction, by using monatomic gas in the space.

17. rThe method of controlling conduction between electrical discharge electrodes which comprises restricting conduction between the electrodes by a gas space comparable to the mean free path of electrons in the gas, in-

creasing the permissible gas pressure in the space by using monatomic gas in said space, and producing conduction between the electrodes in one direction by causing the electrons from one electrode to travel in paths longer than the shortest distance between the electrodes.

18. The method of controlling conduction between electrical discharge electrodes which comprlses restricting phi-lateral, conduction Lemire between'the electrodes by a gas space less than the mean free path of electrons in the gas, increasin the permissible separation of the electrodes y using monatomic gas in said space, and producing unilateral conduction between the electrodes by causing the electrons from one electrode to travel in paths longer than the shortest distance between the electrodes.

19. In electrical apparatus of the type having juxtaposed surfaces s aced sutilciently close together to prevent initiation of substantial conduction directly across the space by normal potential differences, the method of i-ncreasmg the insulating edect of the space which comprises substituting, in lieu of some of the air in the space, a gas having a longer ionizing mean free path.

20. Electrical apparatus of the type having opposed surfaces separated by a space sufficiently short to prevent initiation of substantial conduction directly across the space by potentials high enough to initiate space suciently short to preventinitiatwn of subslantial i conduction directly across the space by potentials high enough to initilll ate conduction across longer gaps, characterized in that the gas in said space` has an ionizing' mean free path suciently long, compared with that of air, to permit a gas pressure many times as high as the maximum air pressure which would inhibit conduction. c 22. Electrical apparatus of the type hav- 1n opposed surfaces separated vby a space su tu ciently short to prevent initiation of substantial conduction directly across the space by potentials high enough to initiate conduction across longergaps, characterized by means for increasing the permissible length of said space over the length in air at the same pressure for. a corresponding degree olf restriction of gaseousconduction, said means comprising gas in said snace having a relatively long ionizing mean free path 4compared with air.

23. A gaseous conduction rectifier employing an arrangement of electrodes in which the cathode functions belowi the temperature at which the operation is dependent upon thermionic emission from the cathode,

CHARLES G, SMITHQ GII 

